In the past the standard way to incorporate a uni-directional drive into such a drive train was to form a ratchet gear in which a central hub was mounted on a shaft and was surrounded by an annulus carrying on its outside the gear teeth which were to mesh with some other gear in the train. Concentricity of the annulus was assured by the sliding bearing surfaces on the outer periphery of the hub and the inner periphery of the ring. There was a pawl and ratchet uni-directional drive linkage between the hub and the ring.
This arrangement was comparatively simple to manufacture and to assemble.
However, in investigating the efficiency of gear trains in the context of winches we have found that that arrangement has a disadvantage which is that, especially because of the very high torque to which such trains are subject when the ratchet gear is the final drive gear before the drum, its efficiency at a time when the pawls are clicking past the ratchet teeth is very low due to high bearing loads on the centering surfaces.